1. Field of the Invention
The present invention relates to the manufacture of cigarette filters, and more particular to the manufacture of a filter rod having a hollow tube extending longitudinally therethrough as an intermediate product in the manufacture of cigarette filters having a smoke flow passage therethrough, and a cigarette filter having the filter rod.
2. Brief Discussion of the Prior Art
Cigarette filters having a smoke flow passage extending longitudinally therethrough, and apparatus for making such filters are known.
Cigarette filters having a longitudinally extending hollow passageway are used to provide a flow of filtered smoke and a separate stream of unfiltered smoke into the smoker's mouth.
By way of example, one such filter and apparatus for manufacturing the filter is shown in U.S. Pat. No. 3,860,011 issued on Jan. 14, 1975 to Vello Norman.
The apparatus of U.S. Pat. No. 3,860,011 includes a garniture funnel and a coaxial hollow mandrel through which a hollow tube is guided into the garniture funnel. The hollow tube is supplied to the hollow tube guide mandrel from a supply reel. The hollow tube supply reel is rotated by a driven wheel in contact with the periphery of the tube supply reel to unwind the tubing from the reel. The unwound tubing passes over a guide roller, around a tensioned take-up roll, and over another guide roller to form a tensional loop of tubing which functions as a reservoir of tubing to accommodate small variations between the speed at which the tubing is unwound from the supply roll and the speed at which the tubing is applied to the filter web in the garniture funnel. In the garniture funnel, the filter material tow is gradually circumferentially wrapped around the hollow tubing.
These are some drawbacks to the heretofore known apparatus of the type disclosed in U.S. Pat. No. 3,860,011. Among these drawbacks is that the apparatus only provides for the hollow tubing being held in place longitudinally in the enwrapping filter material merely by function. Another drawback is that because the hollow tube supplied to the garniture funnel from the tubing supply reel is constantly under tension, it can relatively easily be subjected to a tension greater than its tensile strength causing the hollow tubing to break. In a high volume production facility, the breaking of the supply of hollow tubinig can result in the manufacture of a defective product before the equipment can be shut-down. In addition, in a high volume production facility, equipment down-time is very expensive because of lost production time, the idle time of employees, the expense of getting the equipment back into operation, and over-time expense required to make up production lost during the down-time.
A further drawback is that because the hollow tube is mated with the filter material tow in the garniture funnel under tension, when the filter tow is cut into individual cigarette filters the hollow tube relaxes into the body of the filter. In the event that the tensioned hollow tube is tightly secured to the filter so it will not relax independently of the filter it can occur that the axial force generated by the tensioned hollow tube will cause the filter to bend into a "banana" shape.
The present invention recognizes these drawbacks and provides a solution which is well suited for high volume production of cigarette filters.